The present invention generally relates to heat-exchangers, and more particularly to heat-exchangers of the type including plates arranged side-by-side and mutually parallel.
Heat-exchangers including a plurality of mutually parallel plates, with channels that are adapted to carry at least one heat transfer fluid, are well known in the art. Such parallel plate devices are often formed from a continuous sheet of metal, as a xe2x80x9cfolded-finxe2x80x9d. The plates in such prior art heat-exchangers often consist of metal sheets which delimit a multiple circuit for circulation of two independent fluids, in counterflow, from one end of the exchanger to the other. The plates are often connected to one another at their longitudinal edges by longitudinal braces or the like that are fixed together by a leak-tight wall extending over the entire length and height of the bundle of plates. The plates define a central zone for heat exchange between the fluids.
In some prior art structures, the plates may have one or more corrugated sheets positioned between them, in the central heat transfer and exchange zone, to enhance heat exchange with the plates by increasing surface area and introducing turbulence in the flowing liquids. For example, U.S. Pat. No. 5,584,341, discloses a plate bundle for a heat-exchanger, including a stack of mutually parallel metal heat-exchange plates. Each heat-exchange plate includes smooth-surfaced edges and a corrugated central part, which with the associated heat-exchange plates, forms a double circuit for circulation of two independent fluids in counterflow. The plates are connected to one another at their longitudinal edges by connection means, and comprise a zone of heat transfer and exchange between the fluids. Another zone is formed at the free ends of the plates for inlet and outlet of the fluids. The fluid inlet and outlet zones are formed by the plane ends of the heat-exchange plates.
A significant disadvantage in prior art heat-exchangers of the type described herein above is the inherent thermal impedance, i.e., resistance to thermal conduction through the thickness of the plate, associated with the materials used to form the heat-exchange plates. These prior art heat-exchange plates must have sufficient thickness so as to provide the requisite structural integrity needed for the physical demands that are placed on such devices in normal use. Very often, the heat exchange plates are required to structurally support a portion of the heat exchanger. These design requirements typically require a minimum material thickness (e.g., a material thickness that is some minimum percentage of the plates width or length) that results in a disadvantageous inherent thermal impedance. Material selection is also dictated by this requirement, normally resulting in only metals being selected for the heat-exchange plates. Polymer materials typically exhibit significant dielectric and thermal insulating properties that preclude their use in heat-exchange plates, especially when they are required to provide structural integrity to the device.
There is a need for a heat-exchanger plate structure which will provide the requisite structural integrity needed to survive the physical demands that are placed on such devices in normal use, and which would allow for the use of very thin materials, and even nonmetals, in its fabrication.
The present invention provides a heat-exchanger comprising a fin core formed from a continuous sheet of thermally conductive material that has been folded into alternating flat ridges and troughs defining spaced fin walls having peripheral end edges wherein each of the fin walls has a thickness of about 0.002 to 0.020 inches. In one preferred embodiment the heat-exchanger of the present invention includes at least one air-barrier plate fastened to the flat ridges on a first side of the fin core and a liquid-barrier plate fastened to the flat ridges on a second side of the fin core. A pair of end caps is sealingly fastened to, and covers, the peripheral end edges of the fin core so as to form a plurality of input and exit openings that communicate with the troughs. Advantageously, the fin wall thickness of about 0.002 to 0.020 inches is such that polymer materials may be selected from the group consisting of polyhalo-olefins, polyamides, polyolefins, poly-styrenes, polyvinyls, poly-acrylates, polymethacrylates, polypropylene, polyesters, polystyrenes, polydienes, polyoxides, polyamides and polysulfides, for use in forming the fin core.